1. Field of the Invention
The present invention relates to safe storage for hypodermic and other needles, surgical instruments and sharp tools; more particularly, it relates to a reusable arrangement to protect against accidental contact with the sharp surfaces of needles, invasive medical instruments and other sharp tools.
2. Description of the Related Art
Although accidental wounds due to contact with sharp medical instruments have long plagued health care practitioners, the associated dangers were frequently minimized until the recent spread of the AIDS virus. Over 20 different pathogens are known to have been transmitted by needle-stick injuries. Accordingly, numerous devices have been introduced to minimize or discourage contact between sharp medical devices and their users.
Suitable safety devices must offer favorable structural and operational characteristics. One highly useful structural attribute is compatibility with a range of invasive medical instruments. For example, health care practitioners associate the term "needle" with a variety of devices, including the familiar hypodermic needle, phlebotomy needles, butterfly sets, intravenous catheter stylets, intravenous needle assemblies, prefilled cartridge systems and a variety of other sharp venipuncture instruments. In order to simplify manufacture and encourage industry acceptance, a good design will be usable with a range of related devices.
Other important structural characteristics include low cost of manufacture, a secure locking mode to prevent inadvertent exposure of the sheathed implement, and accurate alignment with the implement to assure reliable operation. The unsheathing operation should be both convenient and resistant to accidental execution (characteristics that tend to oppose one another), while resheathing must be convenient and resistant to mishandling that could cause contact with the instrument. In the specific case of needles, manufacturing difficulties are eased if the sheathing component can be produced with the needle as a unitary construction (e.g., as an extension of the needle hub).
Advantageous operational features include simple and intuitive use, accommodation of frequent sheathings and unsheathings, and the propensity not to interfere--either mechanically or visually--with the operator's use of the unsheathed implement. In the specific case of needles, the user's hands should remain behind the needle during sheathing; it is also useful to provide for fluid discharge after the needle is resheathed.
The prior art includes a large number of needle packaging structures. For example, U.S. Pat. No. 4,867,746 describes a needle shield that exhibits a number of the disadvantages associated with the prior art. The user of this device places the blunt front-end hood against a patient's skin, and proceeds to apply force to drive the needle into the skin at a point anterior to the hood (as shown in FIGS. 4 and 5 of the patent). During this operation, the user is prevented from viewing both the progress of the needle and its entry point. Such observations are important both to maintain precise control over the location of the entry point (which can be critical) and to minimize patient discomfort through choice of the angle of entry. Furthermore, the '746 shield appears to be useful only for needle insertions that are performed at a low angle, since this device relies on the patient's skin to serve as a platform for movement of the shield away from the needle. These limitations render this device particularly unsuitable for use with a large number of surgical instruments (such as scalpels), where the user's line of sight and mechanical freedom cannot be impaired.
U.S. Pat. No. 4,664,259 exemplifies another type of prior-art device that relies on a hinge, rather than flexion, to control withdrawal of the container and consequent exposure of the needle. This device appears to have been designed for one-time needle use (which may or may not be the case in a given clinical context) and during operation may exert force on the needle that could result in its breakage. Like the '746 shield, this device contains no mechanism for assuring non-interference with the user's observation or handling of the needle. The '259 patent does not suggest integral construction with the needle hub.
U.S. Pat. No. 3,658,061 appears to disclose a needle guard comprising an elongated flexible plastic sleeve member with a longitudinal slot adapted to frictionally snap over the entire length of the needle. With this design, the efficacy of the locking mechanism appears to depend on the force exerted on the needle by the edges of the longitudinal sleeve; consequently, achieving a reliable lock might require force that can damage the needle. This design also appears unsuitable for adaptation to surgical instruments other than needles, since its locking mechanism depends on a characteristic curved shape.
All of these devices provide for a single locking mode and appear to contemplate one-handed operation. Few appear to provide for convenient ejection of fluid through the needle when the device is in the closed position.